1. Technical Field
The present invention relates generally to a method for making snack food products that are crisp with blisters (hollow voids or surface bubbles). More particularly, the invention relates to a method of using solid lipid particles for the purpose of controlling the size of blisters on fabricated, expanded snack products.
2. Description of Related Art
Many types of fabricated snack products exist, both baked and fried. These snacks are commonly made by preparing a moist dough comprised of farinaceous materials. The dough is formed, such as by extrusion or by rolls, into a thin sheet. Upon frying or baking, the moisture within the dough is converted to steam, which causes the pieces to expand. With proper control of formulation and baking/frying conditions, known to one skilled in the art, the expanding steam will form voids within the product that will be maintained in the final product. These voids (also known as blisters, or bubbles) result in a less dense snack, which is crisp and appetizing without being too hard and dense to chew.
Under some conditions of baking/frying, however, undesirably large blisters (greater than 1.5 inches in the longest dimension), or bubbles, can form. This is common when frying above 300° F. or baking above 400° F. (or with high air velocities). These large blisters are the result of accumulation of steam between the outer surfaces of the dough pieces during frying or baking. The outer surfaces of the snack piece lose moisture faster than the center of the piece, due to more rapid heat transfer at the surface when frying or baking. When this surface dries sufficiently, it forms a “skin” or “crust” which can prevent escape of steam from the interior of the piece. The trapped steam causes the sides of the dough piece to separate, or delaminate, forming a hollow void. When the void is approximately as large on its surface as the surface area of the piece, this phenomena is commonly referred to as “pillowing.” Excessive blisters, large blisters, and pillowing can detract from the appearance of the snack, and can break, causing holes in the product.
There is considerable prior art directed to controlling the size of blisters and eliminating pillowing. One method is to use low temperatures of baking or frying. These low temperatures result in extended baking/frying times that give the steam time to escape without forming a void. Low bake/fry temperatures, however, usually result in a less crisp, or less “chip-like” texture.
Another means known in the prior art for controlling blister sizes is to use a very thin dough sheet, meaning a sheet of dough having a thickness of less than 0.030 inches. In a thin dough sheet, the skin thickness is not sufficient to prevent steam from escaping from the product, so large voids, or blisters, do not form. Doughs which are sheeted to thicknesses over 0.030 inches, however, are prone to the formation of large, undesirable blisters.
Another means to control blisters is to include large, dry, dense, food particles in the dough. This has previously been detailed by Willard, et al. (U.S. Pat. No. 4,861,609) and is commonly done in tortilla chips by including granular pieces of the corn horny endosperm in the chip. These large, dry particles do not form a cohesive skin so they provide a means for moisture to escape, so as to reduce pillowing and undesirably large blisters. Kunce (U.S. Pat. No. 2,916,378) also details that coarsely ground particles create a discontinuous matrix from which steam can escape. These large, dry particles can detract from the appearance of the product, however, and result in a gritty texture.
Shatila, et al. (U.S. Pat. No. 3,883,671) discloses a method for reducing surface blisters by moistening the surface of the dough pieces after forming, but before frying. This moistening of the surface most likely reduced the formation of a surface “skin” during frying, and thus reduced blister formation. Moistening the surface prior to baking or frying, however, will increase the necessary baking or frying time, as well as altering the texture and appearance of the surface of the snack product.
Mechanical means can also be used to prevent pillowing or minimize blister size. Anderson, et al. (U.S. Pat. No. 2,905,559) avoids pillowing/blistering by perforating the dough sheet with spikes. Willard, et al. (U.S. Pat. No. 4,889,733) uses a rotating bristle brush to form dockering holes. Dockering holes are used in the Willard process to prevent pillowing. Perforating a dough sheet does reduce pillowing/large blisters, by providing holes for the steam to escape through, but results in holes or dimples or the final product, which may be undesirable.
Liepa, et al. (U.S. Pat. No. 3,608,474) teaches confining the dough pieces within a mold to prevent large blisters from forming. This results in a more complicated and expensive manufacturing process.
Carey, et al. (U.S. Pat. No. 5,980,967) discloses a formulation, and hydration procedure, to control blistering in a baked, snack product. Two patents issued to Holm, et al. (U.S. Pat. No. 4,931,303 and U.S. Pat. No. 4,994,295) detail a process of partially drying the surface of a dough layer, thus producing a preform having a dry outer layer and a wet inner layer. Such a procedure results in a more complex manufacturing procedure. The Holm, et al. patents also disclose the procedure of allowing a dough to equilibrate for a few minutes, prior to frying, to control blisters. This is also commonly done in the tortilla manufacturing process. The equilibration time produces more uniform distribution of water within dough, as well as reduces the moisture content by evaporation. This lower moisture content, for example about 25% by weight, uniformly distributed in the snack dough, will create smaller blisters than doughs that have a localized area with high moisture where a blister will form. This equilibration time can be rate limiting, however, and the necessary equilibration time increases with thicker doughs. Similar results can be obtained by excessively pre-baking the product, but this can lead to burnt chips and other unfavorable chip characteristics.
Added ingredients can also be used to reduce blistering. Zimmerman, et al. (U.S. Pat. No. 5,928,700) described adding emulsifiers to fried snack products to reduce pillowing/blistering. Emulsifiers can affect the moisture holding characteristics of the dough, or minimize the moisture necessary to create the dough, both of which can reduce pillowing and large blisters. Zimmerman, et al. state that in their formulation it is important to disperse and thoroughly mix the emulsifier with the other ingredients and it is preferable to dissolve the emulsifier prior to the mixing step. Further, the use of “solid” lipids in Zimmerman only refers to fats that are solids at room temperature but are actually liquefied as part of the mixing/dispersion step. No mention is made of any resultant discrete, solid particles of lipid over 0.010 inches in diameter, and it is noted that the emulsifier had an effect on the texture of the product. Use of lipids in a liquid state in the dough, or lipids which become plastic or liquid during dough formation, or solid lipids in a fine powder will result in a thorough distribution of the lipid throughout the dough during mixing/sheeting with no localized area of discrete lipid larger than 0.010 inches. Such small droplets of liquid, plastic, or fine powder lipid will enhance interaction of the lipid with the starches in the dough, which will alter the texture and properties of the final product. Also, a liquid, plastic, or fine powder lipid, when finely distributed in a dough as small droplets or powder, will reduce pillowing/blistering but will also reduce the formation of the desirable blisters (0.125 inches to 1.5 inches) necessary to create a crispy, chip-like texture and appealing, less “processed” surface appearance. This will result in a less expanded, denser, texture.
Lengerich, et al. (U.S. Pat. No. 4,999,208) used lipid-encapsulated particles to deliver additives in fabricated products. These lipid containing particles were not solid above 100 F, and were not used for blister control.
It should be understood that production of many chip-like products that are ultimately fried or baked often go through a mixing and sheeting process which, depending on ambient conditions, can result in a final dough temperature of between 60° F. and 110° F. Consequently, any lipid added to the dough with a melting point below the temperature level that the product reaches during this stage will melt and become a liquid. In addition, even if a lipid has a complete melting point above 110° F., it may still have significant levels of liquid lipids present below 110° F. Once a lipid becomes a liquid during the mixing/sheeting step, it will disperse in the dough and not only reduce pillowing/large blisters on the product, but also will reduce desirable blister levels. For example, in tortilla chips, it is desirable to have small to medium sized blisters along the surface of the chip. These desirable blisters, typically in the range of 0.125 inches to 1.5 inches in diameter, are reduced when a liquid or solid lipid with a low melting point is added to the dough during dough formation.
Lipids with melting points above such processing temperatures, for example lipids having a melting point above 140° F. and IV values below 15, are available in the prior art, but only in powdered (less than 0.010 inches in largest dimension) or flaked (greater than 0.70 inches in largest dimension) form. The addition of a powdered lipid having a high melting point to a dough can reduce pillowing but will also reduce desirable sized blisters. The addition of lipids with a high melting point in a flake form will resolve the pillowing/large blisters problem while maintaining desirable size blisters. However, lipid flakes cannot be used in products having a thickness between 0.030 inches and 0.055 inches because such flakes typically have a diameter (greater than 0.070 inches) large enough that holes in the product are left when the large lipid flakes are subjected to cooking temperatures by either baking or frying.
Consequently, there exists no acceptable method in the prior art for regulating the size of blisters and reduce pillowing in a snack product having a sheeted or extruded pre-cooked thickness of between 0.030 inches and 0.055 inches that is exposed to pre-cooking processing temperatures from 60° F. to 110° F. In such instances, the prior art does not disclose a successful means of controlling blisters independent of thickness without; 1) the addition or coarse, gritty particles, 2) moistening the surface, 3) mechanical means which produce holes in the product or result in a complicated manufacturing procedure, 4) equilibrating the dough for extended periods of time, 5) or adding lipids in a liquid, plastic, or fine solid powder state which substantially interact with the dough and modify the resultant texture as well as substantially reducing desirable sized blisters.
Thus, a need exists for a method for controlling the blister size in a snack food product having a pre-cooked thickness of 0.030 inches to 0.055 inches with a mixing/sheeting processing step requiring exposure of the product to temperatures from 60° F. to 110° F. Such method should be simple and inexpensive to implement without changing the desirable taste characteristics of the chip.